1. Field of the Invention
The present invention relates to a method and apparatus for estimating a vehicle maneuvering state given by a driver, and a method and apparatus for controlling the running characteristic of a vehicle to adapt the same to the vehicle maneuvering state estimated by the aforementioned estimating method and apparatus.
2. Description of the Related Art
A vehicle is equipped with various apparatuses to improve the traveling stability, maneuverability, riding comfort, etc. of the vehicle.
For instance, a vehicle is provided with an electronic fuel supply controller to optimally control the quantity of fuel supplied to an engine in accordance with the vehicle running state represented by a vehicle speed, the opening degree of an accelerator pedal, etc., an automatic transmission for selecting a gearshift position optimum for the current vehicle running state, and an anti-skid brake system for providing optimum braking power. The vehicle is further equipped with a traction control system for ensuring an optimum slip ratio of driving wheels, a four-wheel steering system for steering rear wheels in the case of turning front-wheels, an active suspension system for variably changing suspension characteristics, and an electric power steering for variably adjusting the steering power.
The vehicle provided with the aforementioned systems features high maneuverability and running stability, and satisfies to a great extent the performance required of a vehicle.
Nevertheless, the driving capability and the inclination in driving vary from one person to another; therefore, the running characteristic required of a vehicle accordingly vary from one driver to another. Moreover, a driver does not constantly require the same vehicle running characteristic. For example, the vehicle running characteristic required by the same driver may vary, depending on whether the driver is driving in an urban area or a mountainous area, or they may vary from day to day.
On the other hand, conventionally, the systems, mounted on the vehicle for controlling the vehicle running characteristic, are operated in accordance with the vehicle driving state indicated by physical quantities such as the vehicle speed and the opening degree of the accelerator. This sometimes makes it difficult to achieve the vehicle running characteristic required by individual drivers.
An apparatus for recognizing the vehicle driving state is also publicly known through unexamined Japanese patent publication no. 2-267030, for instance, which corresponds to U.S. Pat. No. 5,182,710 and European patent application no. 391387. In these publications, the driving state is determined based on the frequency distribution of a plurality of driving parameters, including the opening degree of a throttle valve and engine speed. In other words, based on the plurality of driving parameters, factor analysis is carried out to recognize and determine the driving state such as congested traffic driving, urban area driving, high-speed driving, and sports driving. Based on the recognition result, optimum vehicle control is carried out.
In this publicly known example, however, the frequency-distribution-related parameters only include mean values. This leads to insufficient reliability in the driving state determining result. Moreover, the driving state (sports driving) is determined at the same level as traffic conditions; therefore, it is difficult to determine a proper driving state, i.e., a driver's intent, in response to changes in the traffic conditions.